Observation tower



FIG. 1 is a front isometric view of our new design for an observation tower.

FIG. 2 is a back side elevation view of FIG. 1

FIG. 3 is a front side elevation view of FIG. 1.

FIG. 4 is a left side elevation view of FIG. 1.

FIG. 5 is a right side elevation view of FIG. 1; and,

FIG. 6 is top plan view of FIG. 1.

The elements shown in evenly-spaced broken lines show unclaimed environmental structures and form no part of the claimed design. Dot-dash lines define boundaries of the claimed design and form no part of the claimed design. 

CLAIM The ornamental design for an observation tower, as shown and described. 